Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste

Home , Boiling water reactor, Startup neutron source

Hitachi Review Vol. 63 (2014), No. 9 602

Featured Articles Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste

Tetsushi Hino, Dr. Sci. OVERVIEW: One of the problems with nuclear power generation is the Masaya Ohtsuka, Dr. Eng. accumulation in radioactive waste of the long-lived TRUs generated as Kumiaki Moriya byproducts of the fission of uranium fuel. Hitachi is developing a nuclear reactor that can burn TRU fuel and is based on a BWR design that is Masayoshi Matsuura already in use in commercial reactors. Achieving the efficient fission of TRUs requires that the spectrum of neutron energies in the nuclear reactor be modified to promote nuclear reactions by these elements. By taking advantage of one of the features of BWRs, namely that their neutron energy spectrum is more easily controlled than that of other reactor types, the new reactor combines effective use of resources with a reduction in the load on the environment by using TRUs as fuel that can be repeatedly recycled to burn these elements up.

This article describes the concept behind the INTRODUCTION RBWR along with the progress of its development, NUCLEAR power generation has an important role to as well as its specifications and features. play in both energy security and reducing emissions of carbon dioxide. One of its problems, however, is the accumulation in radioactive waste from the long- RBWR CONCEPT lived transuranium elements (TRUs) generated as Plutonium Breeding Reactor byproducts of the fission of uranium fuel. The TRUs The original concept on which the RBWR is based include many different isotopes with half-lives ranging was the plutonium generation boiling water reactor from hundreds to tens of thousands of years or more. (PGBR) proposed by Takeda and others from Hitachi As a result, the radiotoxicity of TRU-containing in 1988(2). The PGBR produces fissile plutonium (Puf), radioactive waste (a measure of the intensity of a TRU fuel for nuclear power generation containing radiation in terms of the combined effects on people plutonium-239 (239Pu) and plutonium-241 (241Pu), of all radioactive isotopes in the waste) takes around from uranium-238 (238U), the non-fissile isotope that 100,000 years to fall to a level equivalent to that of makes up more than 99% of natural uranium (U). naturally occurring uranium ore. If, on the other hand, Puf breeding means that more Puf is created during the TRUs could be burned up to eliminate them from the burning of the fuel than is provided in the initial the radioactive waste, this time could be reduced to a fuel as a startup neutron source. As it was generally few hundred years(1). assumed at the time that this could only be achieved Work is progressing on the research and using sodium-cooled fast reactors, the PGBR’s ability development of nuclear reactors capable not only of to breed plutonium in a light water reactor made it a eliminating TRUs from waste, but also of reducing ground-breaking proposal. the consumption of uranium by burning TRUs as fuel. To achieve the breeding of plutonium, it is Sodium-cooled fast reactors, which use sodium (Na) necessary to promote the absorption of neutrons by to cool the fuel, are one example. 238U to transmute it into 239Pu. For it to be used in a Hitachi, meanwhile, is working on the development power reactor, it also needs to be able to sustain a of its resource-renewable boiling water reactor fission chain reaction in the nuclear reactor. That is, (RBWR) based on a boiling water reactor (BWR) a higher number of neutrons than in a conventional design that is already in use in commercial reactors. BWR is required to maintain the simultaneous

- 75 - 603 Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste transmutation and fission chain reactions. Typically, it automatically acts to reduce that output. The main the higher the energy of the neutrons that trigger mechanisms for inherent safety in a conventional fission, the more it encourages neutron absorption by BWR are the effect whereby fission is suppressed 238U and the higher, in relative terms, the number of by the greater absorption of neutrons as the fuel neutrons emitted by the fission reaction. Accordingly, temperature increases (Doppler effect), and the effect breeding plutonium requires that the mean neutron whereby higher temperatures promote more coolant energy in the reactor be raised. boiling, which raises the proportional volume of steam In a BWR, the heat from the fuel rods causes (void fraction), reduces the moderation of neutrons, the water (coolant) that flows through the core of a and thereby also suppresses fission. nuclear reactor to boil, thereby removing heat from This latter effect is a consequence of the fact that, the fuel rods. Meanwhile, the coolant also acts to in a conventional BWR, fission is primarily triggered moderate the high energy of the neutrons generated by low energy neutrons (around 0.1 eV). This is by the fission reaction (reduce it down to a low level) because, at low energies, the fission of fissile 235U through repeated collisions between neutrons and and 239, 241Pu tends to become less likely as the neutron the hydrogen nuclei in the coolant. To minimize this energy increases. An indicator that represents this effect, the PGBR reduces the proportional volume relationship between void fraction and likelihood of of coolant in the reactor core by having narrower fission is called the void reactivity coefficient. The coolant channels between fuel rods. Calculations void reactivity coefficient has a negative value in have also demonstrated that the PGBR can achieve a situations where an increase in void fraction makes high neutron energy and enable Pu breeding despite fission less likely, as in a conventional BWR. being a light water reactor by taking advantage of a This relationship reverses at high energies of characteristic of BWRs whereby the boiling of coolant 100 keV or more, where the higher the neutron energy to form steam reduces the density of hydrogen nuclei. the more likely fission is to occur. Accordingly, when the proportion of fission reactions triggered by high- Intrinsic Safety energy neutrons becomes large, as in the PGBR which Nuclear reactors need to exhibit inherent safety, which is intended for plutonium breeding, the effect whereby means that, when the output of a reactor increases due a higher void ratio automatically acts to reduce reactor to some external factor, the nature of its design means output becomes attenuated. Although the Doppler

Turbine building Conventional BWR fuel 155 mm

Reactor building 4 m

Fuel rod Coolant

RBWR fuel Core TRU zone (including Puf) 2.4 m 199 mm Reactor Power plant pressure vessel 194 mm

BWR: boiling water reactor RBWR: resource-renewable BWR TRU: transuranium element Puf: fissile plutonium Fig. 1—RBWR Concept. Apart from the core, the RBWR is largely the same as conventional BWR systems. To achieve effective burning of TRUs, the gaps between fuel rods through which the coolant flows are narrower on the RBWR. Also, the TRUs are contained in two separate zones to ensure inherent safety.

- 76 - Hitachi Review Vol. 63 (2014), No. 9 604

depleted uranium is a plentiful resource that can Rise in thermal output provide the basis of a long-term energy supply. Multi-recycling requires that the isotopic More coolant boiling composition of TRUs in the fuel be kept the same TRU zone (including before and after burning them in the reactor. If the Puf) proportion of fissile isotopes after use is lower, then Low Fewer fission High the amount of these isotopes will diminish each time neutron reactions neutron leakage leakage the fuel is recycled, ultimately resulting in loss of Lower criticality in the reactor. There is also the risk of thermal output Depleted uranium compromising reactor design and operation criteria, zone (no Puf) such as a change in the fuel composition causing Low thermal output High thermal output the void reactivity coefficient to become positive. In addition to having narrower coolant channels, the Fig. 2—Inherent Safety of RBWR. RBWR-AC is able to satisfy a variety of criteria as it A rise in thermal output leads to more coolant boiling and runs through repeated operation cycles by modifying greater neutron leakage, thereby suppressing fission. the coolant flow rate to adjust the neutron energy spectrum during operation and maintain a constant isotopic composition of TRUs in the fuel before and effect still works automatically to reduce output, the after use. PGBR has a positive void reactivity coefficient. Takeda and his team continued their work, and TRU Burner in 1995 proposed the concept of an RBWR actinide One of the advantages of nuclear power generation recycler (RBWR-AC) that combined plutonium is that it has a higher energy density than thermal breeding with a negative void reactivity coefficient(3). and other forms of power generation, meaning that The name of the RBWR derives from its ability to it requires less fuel to produce the same amount of recycle not only plutonium but also the other TRUs electric power. On the other hand, when TRUs are as fuel. A feature of the RBWR-AC is that Puf is used to fuel a nuclear reactor, the percentage of the added as a startup neutron source to the fuel in two initial fuel load burned up in each operation cycle is separate zones (two-zoned core) (see Fig. 1). Because only in the single digits or low teens. Accordingly, the increase in void fraction as the reactor output rises the fuel needs to be recycled many times to burn up a acts to reduce the probability that neutrons will collide large amount of TRUs. with and bounce off hydrogen nuclei, the probability of the neutrons leaving the fuel increases. The idea behind the two-zoned core was to suppress fission by amplifying this effect whereby an increase in void Depleted uranium fraction results in greater neutron leakage (see Fig. 2). Fuel load Multi-recycling Another feature of the RBWR-AC is its multi- recycling capability whereby it can repeatedly recycle Power generation, transmutation TRU formation replaces those the TRUs contained in its own spent fuel (see Fig. 3). consumed. The TRUs consumed by the fission reactions that Same TRU isotopic produce the heat needed to generate electric power are RBWR-AC composition before created by the operation of the reactor itself through and after use the transmutation of depleted uranium. This means that the operating cycle of the RBWR-AC can be Fuel extraction and reprocessing TRUs maintained simply by replenishing it with depleted AC: actinide recycler uranium. Being the byproduct left over after the Fig. 3—Fuel Cycle for RBWR-AC. manufacture of the enriched uranium (which contains Each operation cycle of the RBWR-AC forms its own TRUs to 235 a high proportion of the fissile U isotope) used to replace those consumed during operation while maintaining the fuel conventional commercial light water reactors, same isotopic composition of TRUs before and after use.

- 77 - 605 Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste

Depleted uranium Depleted uranium

Fuel load Fuel load

Power generation, transmutation Replenished from Power generation, transmutation Replenished from other RBWR-TBs light water reactor

Same TRU isotopic RBWR-TB RBWR-TB2 Each cycle has same composition before isotopic composition and after use of TRUs.

Fuel extraction and reprocessing TRUs Fuel extraction and reprocessing TRUs Operation in parallel

RBWR-TB TRUs Provide fuel.

RBWR-TB2

Time Time TB: TRU burner Fig. 5—Fuel Cycle for RBWR-TB2. Fig. 4—Fuel Cycle for RBWR-TB. The TRUs consumed during operation are replenished from the The TRUs consumed during operation are replenished from spent fuel of light water reactors. The RBWR-TB2 operates in the spent fuel of other RBWR-TBs. The fuel is recycled through parallel with a light water reactor to minimize the buildup of progressively fewer reactors until all the TRUs are burned up excess TRUs. apart from those in the final reactor.

Feasibility Study by US Universities Takeda and his team took advantage of the Between 2007 and 2011, three US universities characteristics of the RBWR that allow it to repeatedly (Massachusetts Institute of Technology, University recycle fuel while keeping constant its isotopic of Michigan, and University of California, Berkeley) composition of TRUs and proposed the concept of conducted feasibility studies of RBWR reactors under employing a TRU burner (RBWR-TB), meaning research contracted to the Electric Power Research a reactor that could reduce the amount of TRUs Institute, Inc. (EPRI)(6). Though some differences by burning them up(4), (5). Although the RBWR-TB between the analysis results obtained by Hitachi shares the RBWR-AC’s characteristic of maintaining and the universities need to be evaluated further, a constant isotopic composition of TRUs in the fuel the analyses collectively indicated that the RBWRs before and after use, the process of burning the fuel appeared to be able to achieve their design objectives. reduces the absolute quantity of TRUs. The operation Part of the contracted study included the proposal of cycle is repeated by making up for this loss of TRUs another TRU reactor, the RBWR-TB2, for comparison by supplying fuel from another RBWR-TB. That with sodium-cooled fast reactors. An RBWR-TB2 is, the concept behind the RBWR-TB is to run the operates in parallel with a conventional light water reactor operation cycle with progressively fewer reactors and burns the TRUs in its spent fuel (see Fig. 5). An until all of the TRUs are burned up except for those RBWR-TB2 recycles fuel repeatedly, loading a mixture loaded into the final reactor (see Fig. 4). This presents of fuels comprising the TRUs in both its own and the light a scenario under which the fuel is first used for long- water reactor’s spent fuel. The operation of the RBWR- term energy production in RBWR-ACs, during which TB2 serves to minimize the buildup of excess TRUs. time the TRU fuel is maintained at a constant level. Subsequently, once alternative non-nuclear forms of energy production become available, RBWR-TBs are RBWR SPECIFICATIONS then used to burn up the TRUs and transition away Plant Overview from nuclear power generation without leaving behind The rated thermal output, power output, reactor long-lived radioactive waste. pressure vessel diameter, and core pressure of the

- 78 - Hitachi Review Vol. 63 (2014), No. 9 606

RBWR are the same as the advanced BWR (ABWR), the latest commercial BWR (see Fig. 6). The core has

Follower 720 fuel assemblies and 223 Y-profile control rods. As the fuel assemblies for the RBWR-AC, -TB, and -TB2 all have roughly the same size, their cores can be swapped between each other by exchanging fuel assemblies. The following section describes the latest Neutron (7) absorption specifications for each reactor type . zone Core Fuel Configuration Fig. 7 shows the fuel assemblies for the RBWR-AC, Horizontal cross-section of reactor Y-profile -TB, and -TB2 respectively. The fuel assemblies for control rod the RBWR-AC have upper and lower TRU zones Fuel assembly (with heights of 280 mm and 193 mm), sandwiched between the upper, central, and lower depleted Parameter RBWR ABWR uranium zones (with heights of 70 mm, 520 mm, and Thermal output (MWt) 3,926 3,926 Power output (MWe) 1,356 1,356 280 mm). Neutron absorber zones, meanwhile, are Reactor pressure vessel 7.1 7.1 diameter (m) located respectively above and below the upper and Core pressure (MPa) 7.2 7.2 lower depleted uranium zones. These are provided to No. of fuel assemblies 720 872 Fuel lattice shape Hexagonal lattice Square lattice enhance the output suppression effect by absorbing No. of control rods 223 205 neutrons when a rise in output causes the void fraction Control rod shape Y-profile Cross (+) profile of the coolant to increase, thereby increasing the

ABWR: advanced BWR leakage of neutrons from the fuel zones (TRU and depleted uranium zones). The heights of the depleted Fig. 6—Basic Specifications of RBWR Plant. uranium and TRU zones are determined so as to The rated thermal output, power output, reactor pressure vessel diameter, and core pressure of the RBWR are the same as an maintain the same isotopic composition of TRUs ABWR. A follower is fitted to the top of each control rod to before and after use. prevent water entering the space vacated when the control rod Because the requirement for TRU breeding is lower is withdrawn. on the RBWR-TB and -TB2 TRU burner reactors

Fuel rod diameter: 10.1 mm Fuel rod diameter: 7.4 mm Fuel rod diameter: 7.2 mm Gap between fuel rods: 1.3 mm Gap between fuel rods: 2.0 mm Gap between fuel rods: 2.2 mm

Plenum ...... 500 mm Plenum ...... 500 mm Plenum ...... 500 mm Neutron Follower absorber...... 500 mm Neutron Neutron absorber...... 500 mm Plenum ...... 300 mm absorber...... 500 mm Upper depleted Plenum ...... 300 mm Plenum ...... 300 mm uranium zone...... 70 mm Upper depleted Upper depleted Upper TRU...... 280 mm uranium zone...... 22 mm uranium zone...... 20 mm Central depleted Upper TRU...... 192 mm Upper TRU...... 224 mm uranium zone...... 520 mm Central depleted Central depleted uranium zone...... 560 mm ...... Lower TRU ...... 193 mm uranium zone 560 mm Neutron Lower depleted ...... absorber uranium zone...... 280 mm Lower TRU 219 mm Lower TRU ...... 221 mm zone Neutron absorber...70 mm Neutron absorber...70 mm Neutron absorber...70 mm

194 mm 194 mm 194 mm

RBWR-AC RBWR-TB RBWR-TB2

Fig. 7—RBWR Fuel Assembly. The height of the TRU and depleted uranium zones, the fuel rod diameter, and the gap between fuel rods are adjusted to ensure that the multi-recycling of TRUs can be performed in a way that suits the purpose of each reactor design. As the RBWR-TB and -TB2 TRU burner reactors have less need for TRU formation, their fuel assemblies do not include the lower depleted uranium zone.

- 79 - 607 Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste than it is on the RBWR-AC, their fuel assemblies ratio of fissile TRU isotopes needs to be increased do not have the lower depleted uranium zone. As in somewhat to keep the relative reduction in fissile TRU the RBWR-AC, they have neutron absorber zones isotopes and non-fissile TRU isotopes the same in the above and below the fuel zones. The heights of the RBWR-TB, where the isotopic composition needs to TRU and depleted uranium zones for the RBWR- be kept constant even as the quantity decreases as the TB are also determined so as to maintain the same fuel is burned. The fuel configuration of the RBWR- isotopic composition of TRUs before and after use, TB2, on the other hand, has a higher proportion of as in the RBWR-AC. In the case of the RBWR-TB2, coolant than the RBWR-TB because it is supplied with when the isotopic composition of TRUs in the fuel TRUs in spent fuel from light water reactors with a supplied from light water reactors is the same for high proportion of fissile isotopes. each operation cycle, the heights of the TRU and depleted uranium zones are determined such that the isotopic composition that results after combining the RBWR CORE CHARACTERISTICS RBWR-TB2’s own spent fuel will be the same for Burning uranium in a conventional BWR forms both each operation cycle. fissile and non-fissile TRU isotopes (see Fig. 9). Along with adjusting the heights of the TRU and When using mixed oxide (MOX) fuel that contains depleted uranium zones in the RBWR-AC, -TB, and plutonium and uranium, the fuel ends up with more of -TB2, the balance between consumption and creation the non-fissile isotopes of plutonium and other TRUs of TRUs is also adjusted by modifying the fuel rod than it had when loaded because, whereas the fissile diameter and gaps between fuel rods to adjust the isotopes of plutonium are consumed, the non-fissile neutron energy spectrum (see Fig. 8). In the case isotopes are not. Calculations have demonstrated that of the RBWR-AC, where not only the isotopic the RBWR-TB and -TB2 TRU burner reactors are able composition of TRUs but also their quantity needs to to consume both fissile and non-fissile TRU isotopes be kept constant before and after use, it is necessary to at more than twice the rate they are produced by a increase the mean neutron energy by having the lowest conventional BWR. proportion of coolant of the three designs so that the Fig. 10 shows the dependence of the neutron ratio of fissile TRU isotopes before and after use capture rate and fission reaction rate on neutron (breeding ratio) will be above 1.0. After the RBWR- energy in the nuclear reactor of an RBWR-TB, AC, it is the RBWR-TB that has the next lowest where the neutron capture rate is the proportion of proportion of coolant. This is because the breeding

0.4

Conventional BWR Conventional BWR RBWR-AC 0.2 1 (MOX fuel) (uranium fuel) RBWR-TB Maintain same RBWR-TB2 0 quantity of TRUs. Supply TRUs from light Supply TRUs from other water reactors (high −0.2 proportion of fissile isotopes). 0.5 RBWR-TBs (low proportion RBWR-TB2 of fissile isotopes). Conventional BWR −0.4 before and after use Non-fissile TRU isotopes TRU Non-fissile

Proportion of fissile isotopes Proportion of fissile Without TRU recycling −0.6 RBWR-TB 0 0 1 2 3 −0.8 Proportionate volume (coolant/fuel) −0.8 −0.4 0 0.4 Fissile TRU isotopes TRU formation rate (t/year/reactor) Fig. 8—Proportionate Volume of Coolant in RBWR and Conventional BWR Reactors. MOX: mixed oxide Since the RBWR-AC and -TB need to continue the operation cycle without consuming fissile materials other than those Fig. 9—Rate of Formation and Consumption of TRUs. contained in the fuel discharged from themselves, their water- A negative value indicates that consumption of TRUs results in a to-fuel volume ratios are set lower than those of the RBWR-TB2 reduction in their quantity. The value for conventional BWRs is and conventional BWR. from Ando and Takano(8).

- 80 - Hitachi Review Vol. 63 (2014), No. 9 608

0.35 cases in which a transmutation reaction occurs due to Neutron capture rate 0.30 capture of a neutron and the fission reaction rate is the proportion of cases in which fission occurs(7). Neutron 0.25 capture occurs for a wide range of energies, from low 0.20 energies of around 10−1 eV up to high energies on the 0.15 order of 106 eV. Non-fissile isotopes such as 240Pu and 241 0.10 americium-241 ( Am) are transmuted by neutron Reaction rate (relative) capture into fissile 241Pu and 242Am respectively. 0.05 Also, the direct fission of isotopes like 240Pu and 0.00 241 10−3 10−1 101 103 105 107 Am occurs at high neutron energies in the vicinity 6 Neutron energy (eV) of 10 eV. By using this wide distribution of neutron energies to achieve the fission of non-fissile TRUs, 0.20 Fission reaction rate both by first transmuting them into fissile TRUs and also through direct fission by high-energy neutrons, 0.15 the RBWR can burn up non-fissile TRUs in the same proportion as fissile TRUs and maintain the same 0.10 isotopic composition of TRUs before and after use. Table 1 lists the isotopic composition of TRUs

Reaction rate (relative) 0.05 before and after use and the core characteristics of the RBWR-AC, -TB, and -TB2. When the RBWR-

0.00 AC and -TB are operated to keep the same isotopic 10−3 10−1 101 103 105 107 composition of TRUs in the fuel before and after Neutron energy (eV) use, the quantity of TRUs increases in the case of the Fig. 10—Dependence on Neutron Energy of Neutron Capture RBWR-AC and decreases in the case of RBWR-TB. and Fission Reactions in RBWR-TB Core. When an RBWR-TB2 is loaded with fuel in which Non-fissile TRUs are transmuted into fissile TRUs by the capture the TRUs in its own spent fuel and the spent fuel from of a neutron. a light water reactor are in the same proportion, and

TABLE 1. Change in Isotopic Composition of TRUs during Burning in Reactor This considers the case when spent fuel is left for three years after removal from the reactor to allow radiation and heat generation to diminish. RBWR-AC RBWR-TB RBWR-TB2 Three Three Three TRUs discharged When fuel When fuel When fuel Isotope years after years after years after from light water loaded loaded loaded removal removal removal reactor Np237 0.4 0.4 0.1 0.1 1.9 1.4 6.7 Pu238 2.9 2.9 4.7 4.7 6.3 6.7 2.8 Pu239 43.5 43.5 9.5 9.5 27.7 25.5 48.8 Pu240 36.3 36.3 39.5 39.6 38.5 40.1 23 Pu241 5.1 5.1 4.4 4.4 5.5 5.4 7 Pu242 5.1 5.1 25.4 25.4 9.6 10.1 5 Am241 3.6 3.6 4.7 4.7 5.4 5.4 4.7 Am242m 0.2 0.2 0.2 0.2 0.2 0.2 0 Am243 1.3 1.3 4.7 4.7 2.4 2.4 1.5 Cm244 1.1 1.1 4.1 4 1.8 2 0.5 Cm245 0.4 0.4 1.2 1.2 0.5 0.6 0 Cm246 0.1 0.1 1 1 0.2 0.2 0 Cm247 0 0 0.2 0.2 0 0 0 Cm248 0 0 0.2 0.2 0 0 0 Cm249 0 0 0.1 0.1 0 0 0 Puf (t) 1.94 1.96 1.14 1.06 2.06 1.74 0.32 TRU (t) 3.99 4.03 8.18 7.62 6.2 5.63 0.58 Np: neptunium Pu: plutonium Am: americium Cm: curium

- 81 - 609 Light Water Reactor System Designed to Minimize Environmental Burden of Radioactive Waste under conditions in which the isotopic composition of REFERENCES TRUs remains the same in each cycle, the quantity of (1) Working Group on Technologies for Separation of Nuclides TRUs decreases as the fuel is burned. and Nuclear Transmutation, Nuclear Science and Technology Calculations have also demonstrated that all of Committee, Ministry of Education, Culture, Sports, Science the reactor types have a negative void reactivity and Technology, http://www.mext.go.jp/b_menu/shingi/ gijyutu/gijyutu2/070/index.htm in Japanese. (7) coefficient . (2) R. Takeda et al., “A Conceptual Core Design of Plutonium Generation Boiling Water Reactor,” Proc. of the 1988 International Reactor Physics Conference 3, p. 119 (1988). CONCLUSIONS (3) R. Takeda et al., “General Features of Resource-Renewable This article has provided an overview and described BWR (RBWR) and Scenario of Long-term Energy Supply,” the latest specifications of the RBWR, a reactor that Proc. of International Conference on Evaluation of Emerging, can recycle as fuel the TRUs formed in nuclear power Nuclear Fuel Cycle Systems 1, p. 938 (1995). generation to provide a long-term supply of energy (4) R. Takeda et al., “BWRS for Long-term Energy Supply and for Fissioning Almost All Transuranium,” Proc. of GLOBAL while also preventing the TRUs from becoming 2007, p. 1725 (2007). radioactive waste that will continue to emit radiation (5) R. Takeda et al., “RBWRs for Fissioning Almost All Uranium for a long time. and Transuraniums,” Transactions of the American Nuclear Hitachi intends to continue development work Society 107, p. 853 (2012). aimed at commercializing the RBWR, seeing it as a (6) “Technical Evaluation of the Hitachi Resource-Renewable valuable option, based on proven BWR technology, BWR (RBWR) Design Concept,” EPRI Technical Report for meeting expectations for the long-term supply 1025086 (2012). of energy from nuclear power while also solving the (7) T. Hino et al., “Core Designs of RBWR (Resource-renewable BWR) for Recycling and Transmutation of Transuranium industry’s problem of how to deal with TRUs. Elements - an Overview,” Proc. of ICAPP 2014, Paper 14271 (2014). (8) Y. Ando and H. Takano, “Evaluation of Isotopes Present in Spent Fuel from Light Water Reactors,” JAERI-Research 99-004 (1999) in Japanese.

ABOUT THE AUTHORS

Tetsushi Hino, Dr. Sci. Masaya Ohtsuka, Dr. Eng. Nuclear Energy Systems Research Department, Hitachi Research Laboratory, Hitachi, Ltd. He is Hitachi Research Laboratory, Hitachi, Ltd. He is currently engaged in research and development of currently engaged in research and development of nuclear power systems. Dr. Ohtsuka is a Fellow of core systems for boiling water reactors. Dr. Hino is a the AESJ, and a member of the ANS and The Japan member of the Atomic Energy Society of Japan (AESJ) Society of Mechanical Engineers (JSME). and the American Nuclear Society (ANS).

Kumiaki Moriya Masayoshi Matsuura Business Planning Division, Hitachi Works, Hitachi- Nuclear Plant Engineering Department, Hitachi GE Nuclear Energy, Ltd. He is currently engaged Works, Hitachi-GE Nuclear Energy, Ltd. He is in making improvements to BWR technology and currently engaged in the design of nuclear power developing future BWRs. Mr. Moriya is a member of plant systems and management of the next-generation the AESJ and The Physical Society of Japan. reactor project. Mr. Matsuura is a member of the AESJ.

- 82 -